1. Field of the Invention
This invention relates to a polyamide composite material and a method for preparing the same, more particularly to a polyamide composite material having excellent mechanical properties and heat resistance and improved dye-affinity and whitening resistance or anti-blooming property during stretching, and a method for preparing the same.
2. Background Invention
There have been practiced to mix and knead inorganic materials such as calcium carbonate, clay minerals, mica, etc. with organic polymer materials including polyamides, in order to improve various properties, particularly mechanical properties thereof.
However, with respect to materials including polyamides, since these inorganic materials cannot ultrafinely be dispersed into polyamide only by mixing and kneading them, a polyamide composite having satisfactory properties has not been obtained.
There has been practiced the method in which a polyamide composite is produced by choosing clay minerals, particularly a clay mineral comprising a layered silicate, as an inorganic material, beforehand making it into a composite with organic compounds such as amino acid, nylon salt, etc., and polymerizing a monomer in the presence of such a composite to produce a polyamide composite comprising the polyamide firmly bound to said composite, in order to enhance affinity or bonding strength between the polyamides and inorganic materials (see Japanese Patent Publication No. 35211/1983).
However, according to the above method, i.e. the polymerization method, since the polyamide composite is obtained by polymerizing the monomer, the end amino groups in the polyamide are consumed during the polymerization reaction step, resulting in blocking of the end amino group. As a result, only polyamide composite materials having insufficient dye-affinity, coating property and printing property have been obtained.
In the above preparation method, further, since the clay minerals act as a terminator, it was difficult to efficiently, economically produce a polyamide/layered silicate composite material of high viscosity type and a polyamide composite material containing layered silicate at high content. In the above conventional method, also, undesirable incorporation of inorganic materials during the polymerization step may cause a drawback that a large amount of a changing loss occurs when the starting materials for polymerization are changed.
In the above conventional method, further, in the instance where the clay/organic material composite in which amino acid or nylon salt is bonded to the clay does not have swellability with a monomer for polymer compounds constituting the composite material or a mixture of the monomer and a dispersion medium, it was difficult to uniformly disperse the composite into the polymer compounds.
As described above, the conventional polyamide composite material, in which the layered silicate is uniformly dispersed therein, had drawbacks that obtained were only a polyamide composite material of which the end amino groups, which can impart dye-affinity, printing property and whitening resistance to the polyamide, are blocked. In the conventional preparation method, the production efficiency is low, and, with the increase of the content of the layered silicate, the production efficiency will become lower, also, the layered silicate acts as an end blocking agent and thus it is difficult to efficiently increase the polymerization degree.
Further, it is difficult or impossible to produce diaminedicarboxylic acid type polyamide containing a layered silicate from conventional diamine-dicarboxylate (see Japanese Unexamined Patent Publication No. 221125/1988).